Development of an ammunition cartridge, which contained all the components necessary to fire a projectile from a firearm in one object, revolutionized firearms technology. Ammunition cartridges include a metallic case, preferably brass, fitted to accept a primer of an appropriate size, gunpowder, and a projectile. More commonly, a cartridge is referred to as a “bullet” even though the projectile, the bullet, is but one element of an ammunition cartridge. One of the reasons for this clarification is that ammunition cartridges are made in different sizes. For example, a brass case may be a particular size, provide a primer pocket for receiving a primer of a particular size, have an internal volume of a specific size to receive gun powder, and may further accept a bullet of a particular size. Ammunition cartridges are typically referred to by distinguishing characteristics of the cartridge. For example, cartridges that include bullets that are 0.22 inches in diameter (e.g., .22 caliber) are typically referred to as “twenty twos.”
One problem with this nomenclature is that there are a number of different .22 caliber ammunition cartridges. Thus, these other cartridges are combined with another word to uniquely identify the specific cartridge being referred to. For example, 22 Short, 22 Long, 22 Long Rifle (which is typically referred to and understood as the “twenty two”), 223 Remington, 220 Swift, are all .22 caliber bullets although the dimensions of the brass case require differences in the guns that will chamber these various rounds. Accordingly, other nomenclatures have been developed to refer to a particular .22 caliber. For example, one person may explain to another that a particular rifle is a 22 Short which means that a 22 Long Rifle cartridge will not fit in the rifle because of the differences in a size of the casing associated with the round (the 22 Long Rifle implements a physically longer case than a 22 Short).
To further complicate matters, commonly known and understood terms in the United States may also have international designations, which are typically identified in millimeters. For example, a 5.56 mm bullet is a .223 caliber bullet. With relatively minor differences, any firearm that accepts a 5.56 mm NATO cartridge will also accept a .223 Remington cartridge (but not necessarily the other way around). Hundreds, if not thousands of different cartridges have been developed for a host of different uses. Many of these cartridges are derivatives of other more “standard” cartridges. A “standard” cartridge is typically one that has been used by a military as a general issue caliber or refers to a cartridge that has been standardized by Sporting Arms and Ammunition Manufacturers' Institute (SAAMI). Examples of standard cartridges may include 5.56×45 mm NATO (223 Remington in the United States), 30-06 Springfield, 7.62×51 mm (NATO—which in the United States is referred to as a .308, 7.62×39 (developed by the former Soviet Union), 9 mm, 45 ACP, and a number of others. Wildcatters, as they are known, are people who experiment on different caliber cartridges to examine the ballistics of each cartridge they have developed. Several “wildcat” cartridges have been developed into readily available cartridges today.
One difficult aspect of wildcat cartridges is that standard calibers, case dimensions, primer types, gunpowder loads, and etc. are not readily available to other shooters. Thus, only the very best wildcat cartridges become standardly available cartridges, frequently because the ballistics of a particular wildcat cartridge surpass what is currently available in standard cartridges. Many of these wildcat cartridges are “necked down” versions of standard cartridges. A necked down cartridge is one that was originally meant for a larger bullet but whose neck size has been reduced to accept a smaller bullet. For example, the 7.62×39 case has been necked down (among other changes) to accept a 6.5 mm bullet, to make a cartridge known as a 6.5 Grendel. Other examples of necked down cartridges include the 220 Swift (a necked down 6 mm Lee Navy), any of the cartridges known as “short magnums,” 17 HMR, 270 Winchester, 243 Winchester, and a host of others.
Cartridges, however, are only one aspect of successfully firing a projectile into a target. A firearm must be developed to fire each specific cartridge and include a chamber which virtually identically accepts the outer dimensions of the cartridge while also providing a barrel that matches the dimensions of the bullet. This can be a challenging feat based on the “neck angle” of the cartridge. The “neck angle” is the taper of a neck of a case from the body up to the top of the case. A wider body with a smaller bullet, results in a more tapered neck angle while a narrower body with a bigger bullet results in less neck angle. In necked down cartridges, neck angle can be a substantial problem not only in ensuring a cartridge fits in a chamber of a firearm but also in ensuring cartridges can be fed into the chamber of the firearm. SAAMI typically defines and accepts standard dimensions for wildcat cartridges to become a standardly accepted cartridge.
Militaries, around the world, also perform ballistics research on new rounds that are developed for military use. Both cartridges and firearms are developed to “military specifications,” which is more commonly known as “milspec.” Milspec and SAAMI standards may not be identical in every case, although since many SAAMI standards were developed from military rounds, many milspec and SAAMI standards are identical.
Modern sporting rifles, also known as “Armalite Rifles” or “AR” rifles are typically built to military specifications. AR rifles are highly desirable because they are highly customizable to meet a shooter's particular interests and needs. Thus, the parts for AR rifles are perfectly interchangeable regardless of what manufacturer developed the part, so long as the parts are built to milspec standards. The AR rifle includes a number of parts, such parts referred to as an “upper,” a “lower,” and a “barrel.” For manufacturers, it is undesirable to manufacture any parts for a modern sporting rifle that are not interchangeable with parts made by other manufacturer because the shooting public simply will not buy non-standardized parts.
An AR lower contains the trigger for the rifle and accepts magazines for feeding cartridges with bullets into the AR upper which are fired through the barrel. Thus, magazines must also be built to be milspec (e.g., have appropriate dimensions to feed into a milspec AR lower). However, since the advent of the AR style rifle in 1959, modern shooting enthusiast have developed AR style rifles in different calibers, again to meet the needs of a particular shooting application for a particular person. Initially, the AR-5, AR-10, and AR-15 rifles were developed which fired a 22 Hornet cartridge, a 308 (7.62×51 NATO) cartridge, and a 223 Remington (5.56×45 NATO) cartridge. Since then, AR style rifles have been chambered to use a large number of other cartridges. However, it has been a substantial challenge to develop magazines that reliably feed ammunition in to certain AR implementations. One particularly difficult problem has been in developing milspec magazines for necked down calibers, particularly in non-metallic magazines.
Metallic magazines have been developed for use with AR style rifles which index each cartridge in the magazine based on the bottom of the case or on the body of the case but forgo many of the benefits of a non-metallic magazine. However, many non-metallic magazines typically index each cartridge in the magazine on the neck of the case which, with necked down cases has been a significant problem.
It is, therefore, one object of this disclosure to provide a cartridge magazine that provides a milspec cartridge magazine. It is another object of this disclosure to provide a milspec cartridge magazine that reliably feeds necked down cartridges into an AR style rifle. It is a further object of this disclosure to provide a cartridge magazine that is a milspec, non-metallic, and reliably feeds necked down cartridges into an AR style rifle.